Non-metallic barrels of fiber-reinforced thermosetting resin are primarily employed today for recoil-less weapons such as the rocket launcher or blow-back type which are equipped with single use disposable barrels. As far as we are aware, these barrels are always smooth-bored.
However, primarily in the patent literature, a number of different proposals have already been presented for methods of producing light, rifled barrels by encasing a thin-walled, interiorly rifled steel tube with a sufficiently thick outer layer of a fiber-reinforced thermosetting resin. However, the method is expensive, since the inner metal tube must be worked and rifled in the usual way and, moreover, it would probably be difficult to avoid problems caused by the different expansion coefficients of the metal tube and the surrounding outer reinforcing layer.
Moreover, there is at least one prior art proposal for a method of producing rifled, non-metallic barrels of a composite material of a corresponding type.
Thus, U.S. Pat. No. 4,485,721 describes a method of producing non-metallic, rifled, fiber-reinforced barrels on a rotary mandrel provided with a number of helically arranged grooves, the grooves being first completely filled with a "yarn" impregnated with a thermosetting plastic material, or ropes of carbon fiber which extend in the longitudinal direction of the grooves, whereafter an additional fiber material impregnated with a thermosetting plastic material is wound about the mandrel, either in the form of thread or textile material, until a tube of desired thickness has been attained, whereafter the plastic material, which, according to the above patent may for instance consist of an epoxy resin, is cured, the thus obtained tube being then removed from the mandrel. Concerning the grooves in the mandrel, which would thus provide the lands of the finished barrel, this patent discloses that these may preferably be substantially rectangular in cross-section.
If the method disclosed in the above patent functions satisfactorily, the thus obtained barrel would then have riflings of virtually rectangular cross-section, and display, on the one hand, a first axial reinforcement extending in the longitudinal direction of the lands, and, on the other hand, a substantially peripheral reinforcement.